25

2016

Professor Grant R. Bigg, author of Icebergs has worked with industry on iceberg and sea-ice related topics since 2007, here he talks about climate change in the polar regions and discusses how the the differences in Arctic/Antarctic geography leads to varied responses in the arctic regions.

How is climate change affecting Polar Regions? Are there different effects at each Pole?

The Polar Regions have been, and are likely to continue to be, one of the main regions seeing major environmental change as a result of greenhouse warming. The main reason for this is an ice-albedo feedback – the more ice melts, the darker the exposed surface becomes, allowing more solar radiation to be absorbed, thus warming the surface more and continuing the process. Thus, the main climate change in the Polar Regions is through warming of both the atmosphere and the ocean. Nevertheless, due to the very different geography of the Arctic and Antarctic, they are responding to global change in very different ways. In the Arctic, sea-ice cover is reducing increasingly rapidly, particularly in summer, leading to warmer, and more productive, oceans. Arctic ice sheets and glaciers are reducing, with more freshwater entering the ocean, raising sea level. The surrounding continents are also mostly warming, leading to increases in river flows from more rainfall, and decreases in permafrost cover. In the Antarctic, in contrast, the atmospheric warming has been more geographically restricted, to the Antarctic Peninsula, although ocean warming is having an impact on enhancing under-ice melting of the ice shelves in west Antarctica. Indeed, while sea-ice in the Antarctic is highly variable from year to year, there has been a slight increasing trend in recent years. This may be a feedback from warming leading to more freshwater input to the ocean, making the ocean freeze more easily.

How might changes at the Poles affect global climate/ocean currents?

The most direct changes to global climate and ocean currents are likely to be from change in the Arctic, at least for the next few decades. The warming Arctic seas may already be enhancing heat fluxes to the atmosphere so as to produce more weather variability and extremes, and at times colder continents as a result of changes to atmospheric air flow. In contrast, the increasing flux of meltwater to the ocean may be decreasing the deep convection in the ocean, slowly decreasing the strength of the global meridional overturning circulation. If so, this would lead to a decrease in the movement of warm water poleward in the North Atlantic Drift. The world is beginning a major environmental experiment with greenhouse gas emissions, and the current climate models are not unanimous in their predictions of the details of future perturbations of climate.

Grant R. Bigg, author of Icebergs, 2015 is Professor of Earth System Science in the Department of Geography at the University of Sheffield, and prior to this was Head of the Department of Geography at the same university. He won the Gordon Manley Weather Prize of the Royal Meteorological Society i...